udp, passt: Introduce socket packet buffer, avoid getsockname() for UDP

This is in preparation for scatter-gather IO on the UDP receive path:
save a getsockname() syscall by setting a flag if we get the numbering
of all bound sockets in a strict sequence (expected, in practice) and
repurpose the tap buffer to be also a socket receive buffer, passing
it down to protocol handlers.

Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

icmp.c

@@ -38,9 +38,10 @@
  * @c:		Execution context
  * @s:		File descriptor number for socket
  * @events:	epoll events bitmap
+ * @pkt_buf:	Buffer to receive packets, currently unused
  * @now:	Current timestamp, unused
  */
-void icmp_sock_handler(struct ctx *c, int s, uint32_t events,
+void icmp_sock_handler(struct ctx *c, int s, uint32_t events, char *pkt_buf,
 		       struct timespec *now)
 {
 	struct in6_addr a6 = { .s6_addr = {    0,    0,    0,    0,
@@ -53,6 +54,7 @@ void icmp_sock_handler(struct ctx *c, int s, uint32_t events,
 	ssize_t n;
 
 	(void)events;
+	(void)pkt_buf;
 	(void)now;
 
 	n = recvfrom(s, buf, sizeof(buf), MSG_DONTWAIT,

icmp.h

@@ -3,7 +3,7 @@
 
 struct ctx;
 
-void icmp_sock_handler(struct ctx *c, int s, uint32_t events,
+void icmp_sock_handler(struct ctx *c, int s, uint32_t events, char *pkt_buf,
 		       struct timespec *now);
 int icmp_tap_handler(struct ctx *c, int af, void *addr,
 		     struct tap_msg *msg, int count, struct timespec *now);

passt.c

@@ -60,6 +60,9 @@
 #define TAP_BUF_FILL		(TAP_BUF_BYTES - ETH_MAX_MTU - sizeof(uint32_t))
 #define TAP_MSGS		(TAP_BUF_BYTES / sizeof(struct ethhdr) + 1)
 
+#define PKT_BUF_BYTES		MAX(TAP_BUF_BYTES, SOCK_BUF_BYTES)
+static char pkt_buf		[PKT_BUF_BYTES];
+
 #define TIMER_INTERVAL		MIN(TCP_TIMER_INTERVAL, UDP_TIMER_INTERVAL)
 
 /**
@@ -530,8 +533,6 @@ static int tap6_handler(struct ctx *c, struct tap_msg *msg, size_t count,
 	return 1;
 }
 
-static char tap_buf[TAP_BUF_BYTES];
-
 /**
  * tap_handler() - Packet handler for tap file descriptor
  * @c:		Execution context
@@ -544,7 +545,7 @@ static int tap_handler(struct ctx *c, struct timespec *now)
 	struct tap_msg msg[TAP_MSGS];
 	int msg_count, same, i;
 	struct ethhdr *eh;
-	char *p = tap_buf;
+	char *p = pkt_buf;
 	ssize_t n, rem;
 
 	while ((n = recv(c->fd_unix, p, TAP_BUF_FILL, MSG_DONTWAIT)) > 0) {
@@ -615,7 +616,7 @@ static int tap_handler(struct ctx *c, struct timespec *now)
 			}
 		}
 
-		p = tap_buf;
+		p = pkt_buf;
 	}
 
 	if (n >= 0 || errno == EINTR || errno == EAGAIN || errno == EWOULDBLOCK)
@@ -660,11 +661,11 @@ static void sock_handler(struct ctx *c, int s, uint32_t events,
 	debug("%s: packet from socket %i", getprotobynumber(proto)->p_name, s);
 
 	if (proto == IPPROTO_ICMP || proto == IPPROTO_ICMPV6)
-		icmp_sock_handler(c, s, events, now);
+		icmp_sock_handler(c, s, events, pkt_buf, now);
 	else if (proto == IPPROTO_TCP)
-		tcp_sock_handler(c, s, events, now);
+		tcp_sock_handler( c, s, events, pkt_buf, now);
 	else if (proto == IPPROTO_UDP)
-		udp_sock_handler(c, s, events, now);
+		udp_sock_handler( c, s, events, pkt_buf, now);
 }
 
 /**

passt.h

@@ -14,6 +14,8 @@ struct tap_msg {
 	size_t l4_len;
 };
 
+#define SOCK_BUF_BYTES		(ETH_MAX_MTU * 4)
+
 #include "icmp.h"
 #include "tcp.h"
 #include "udp.h"
@@ -62,5 +64,5 @@ struct ctx {
 
 	struct icmp_ctx icmp;
 	struct tcp_ctx tcp;
-	struct tcp_ctx udp;
+	struct udp_ctx udp;
 };

tcp.c

@@ -1402,14 +1402,17 @@ static void tcp_connect_finish(struct ctx *c, int s)
  * @c:		Execution context
  * @s:		File descriptor number for socket
  * @events:	epoll events bitmap
+ * @pkt_buf:	Buffer to receive packets, currently unused
  * @now:	Current timestamp
  */
-void tcp_sock_handler(struct ctx *c, int s, uint32_t events,
+void tcp_sock_handler(struct ctx *c, int s, uint32_t events, char *pkt_buf,
 		      struct timespec *now)
 {
 	socklen_t sl;
 	int accept;
 
+	(void)pkt_buf;
+
 	if (tc[s].s == LAST_ACK) {
 		tcp_send_to_tap(c, s, ACK, NULL, 0);
 		tcp_close_and_epoll_del(c, s);

tcp.h

@@ -5,7 +5,7 @@
 
 struct ctx;
 
-void tcp_sock_handler(struct ctx *c, int s, uint32_t events,
+void tcp_sock_handler(struct ctx *c, int s, uint32_t events, char *pkt_buf,
 		      struct timespec *now);
 int tcp_tap_handler(struct ctx *c, int af, void *addr,
 		    struct tap_msg *msg, int count, struct timespec *now);

udp.c

@@ -124,25 +124,69 @@ static void udp_sock_handler_local(struct ctx *c, int af, void *sa,
 	}
 }
 
+/**
+ * udp_sock_name() - Get address family and port for bound UDP socket
+ * @c:		Execution context
+ * @s:		File descriptor number for socket
+ * @port:	Local port, set on return, network order
+ *
+ * Return: address family, AF_INET or AF_INET6, negative error code on failure
+ */
+static int udp_sock_name(struct ctx *c, int s, in_port_t *port)
+{
+	if (!c->udp.fd_in_seq) {
+		struct sockaddr_storage sa;
+		socklen_t sl;
+
+		sl = sizeof(sa);
+		if (getsockname(s, (struct sockaddr *)&sa, &sl))
+			return -errno;
+
+		if (sa.ss_family == AF_INET) {
+			*port = ((struct sockaddr_in *)&sa)->sin_port;
+			return AF_INET;
+		}
+
+		if (sa.ss_family == AF_INET6) {
+			*port = ((struct sockaddr_in6 *)&sa)->sin6_port;
+			return AF_INET6;
+		}
+
+		return -ENOTSUP;
+	}
+
+	if (c->v4 && c->v6) {
+		*port = htons((s - c->udp.fd_min) / 2);
+		return ((s - c->udp.fd_min) % 2) ? AF_INET6 : AF_INET;
+	}
+
+	*port = htons(s - c->udp.fd_min);
+	return c->v4 ? AF_INET : AF_INET6;
+}
+
 /**
  * udp_sock_handler() - Handle new data from socket
  * @c:		Execution context
  * @s:		File descriptor number for socket
  * @events:	epoll events bitmap
+ * @pkt_buf:	Buffer to receive packets, currently unused
  * @now:	Current timestamp
  */
-void udp_sock_handler(struct ctx *c, int s, uint32_t events,
+void udp_sock_handler(struct ctx *c, int s, uint32_t events, char *pkt_buf,
 		      struct timespec *now)
 {
 	struct in6_addr a6 = { .s6_addr = {    0,    0,    0,    0,
 					       0,    0,    0,    0,
 					       0,    0, 0xff, 0xff,
 					       0,    0,    0,    0 } };
-	struct sockaddr_storage sr, sl;
+	struct sockaddr_storage sr;
 	socklen_t slen = sizeof(sr);
 	char buf[USHRT_MAX];
 	struct udphdr *uh;
 	ssize_t n;
+	int af;
+
+	(void)pkt_buf;
 
 	if (events == EPOLLERR)
 		return;
@@ -153,13 +197,10 @@ void udp_sock_handler(struct ctx *c, int s, uint32_t events,
 		return;
 
 	uh = (struct udphdr *)buf;
+	af = udp_sock_name(c, s, &uh->dest);
 
-	if (getsockname(s, (struct sockaddr *)&sl, &slen))
-		return;
-
-	if (sl.ss_family == AF_INET) {
+	if (af == AF_INET) {
 		struct sockaddr_in *sr4 = (struct sockaddr_in *)&sr;
-		struct sockaddr_in *sl4 = (struct sockaddr_in *)&sl;
 
 		if (ntohl(sr4->sin_addr.s_addr) == INADDR_LOOPBACK ||
 		    ntohl(sr4->sin_addr.s_addr) == INADDR_ANY)
@@ -167,19 +208,16 @@ void udp_sock_handler(struct ctx *c, int s, uint32_t events,
 
 		memcpy(&a6.s6_addr[12], &sr4->sin_addr, sizeof(sr4->sin_addr));
 		uh->source = sr4->sin_port;
-		uh->dest = sl4->sin_port;
 		uh->len = htons(n + sizeof(*uh));
 
 		tap_ip_send(c, &a6, IPPROTO_UDP, buf, n + sizeof(*uh));
-	} else if (sl.ss_family == AF_INET6) {
+	} else if (af == AF_INET6) {
 		struct sockaddr_in6 *sr6 = (struct sockaddr_in6 *)&sr;
-		struct sockaddr_in6 *sl6 = (struct sockaddr_in6 *)&sl;
 
 		if (IN6_IS_ADDR_LOOPBACK(&sr6->sin6_addr))
 			udp_sock_handler_local(c, AF_INET6, sr6, now);
 
 		uh->source = sr6->sin6_port;
-		uh->dest = sl6->sin6_port;
 		uh->len = htons(n + sizeof(*uh));
 
 		tap_ip_send(c, &sr6->sin6_addr, IPPROTO_UDP,
@@ -363,17 +401,23 @@ int udp_tap_handler(struct ctx *c, int af, void *addr,
  */
 int udp_sock_init(struct ctx *c)
 {
+	int s, prev = -1;
 	in_port_t port;
-	int s;
 
 	c->udp.fd_min = INT_MAX;
 	c->udp.fd_max = 0;
+	c->udp.fd_in_seq = 1;
 
 	for (port = 0; port < USHRT_MAX; port++) {
 		if (c->v4) {
 			if ((s = sock_l4(c, AF_INET, IPPROTO_UDP, port)) < 0)
 				return -1;
 
+			if (c->udp.fd_in_seq && prev != -1 && s != prev + 1)
+				c->udp.fd_in_seq = 0;
+			else
+				prev = s;
+
 			up4[port].s = s;
 		}
 
@@ -381,6 +425,11 @@ int udp_sock_init(struct ctx *c)
 			if ((s = sock_l4(c, AF_INET6, IPPROTO_UDP, port)) < 0)
 				return -1;
 
+			if (c->udp.fd_in_seq && prev != -1 && s != prev + 1)
+				c->udp.fd_in_seq = 0;
+			else
+				prev = s;
+
 			up6[port].s = s;
 		}
 	}
@@ -424,7 +473,8 @@ static void udp_timer_one(struct ctx *c, int af, in_port_t p,
 	if (s != -1) {
 		epoll_ctl(c->epollfd, EPOLL_CTL_DEL, s, NULL);
 		close(s);
-		sock_l4(c, af, IPPROTO_UDP, p);
+		if (sock_l4(c, af, IPPROTO_UDP, p) != s)
+			c->udp.fd_in_seq = 0;
 	}
 }
 

udp.h

@@ -3,7 +3,7 @@
 
 #define UDP_TIMER_INTERVAL		1000 /* ms */
 
-void udp_sock_handler(struct ctx *c, int s, uint32_t events,
+void udp_sock_handler(struct ctx *c, int s, uint32_t events, char *pkt_buf,
 		      struct timespec *now);
 int udp_tap_handler(struct ctx *c, int af, void *addr,
 		    struct tap_msg *msg, int count, struct timespec *now);
@@ -14,11 +14,13 @@ void udp_timer(struct ctx *c, struct timespec *ts);
  * struct udp_ctx - Execution context for UDP
  * @fd_min:		Lowest file descriptor number for UDP ever used
  * @fd_max:		Highest file descriptor number for UDP ever used
+ * @fd_in_seq:		1 if all socket numbers are in sequence, 0 otherwise
  * @timer_run:		Timestamp of most recent timer run
  */
 struct udp_ctx {
 	int fd_min;
 	int fd_max;
+	int fd_in_seq;
 	struct timespec timer_run;
 };
 

util.c

@@ -189,11 +189,6 @@ int sock_l4(struct ctx *c, int af, uint16_t proto, uint16_t port)
 		return -1;
 	}
 
-	CHECK_SET_MIN_MAX_PROTO_FD(proto, IPPROTO_ICMP,		icmp,	fd);
-	CHECK_SET_MIN_MAX_PROTO_FD(proto, IPPROTO_ICMPV6,	icmp,	fd);
-	CHECK_SET_MIN_MAX_PROTO_FD(proto, IPPROTO_TCP,		tcp,	fd);
-	CHECK_SET_MIN_MAX_PROTO_FD(proto, IPPROTO_UDP,		udp,	fd);
-
 	if (proto == IPPROTO_ICMP || proto == IPPROTO_ICMPV6)
 		goto epoll_add;
 
@@ -207,16 +202,29 @@ int sock_l4(struct ctx *c, int af, uint16_t proto, uint16_t port)
 		setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY, &one, sizeof(one));
 	}
 
+	CHECK_SET_MIN_MAX_PROTO_FD(proto, IPPROTO_ICMP,		icmp,	fd);
+	CHECK_SET_MIN_MAX_PROTO_FD(proto, IPPROTO_ICMPV6,	icmp,	fd);
+	CHECK_SET_MIN_MAX_PROTO_FD(proto, IPPROTO_TCP,		tcp,	fd);
+	CHECK_SET_MIN_MAX_PROTO_FD(proto, IPPROTO_UDP,		udp,	fd);
+
 	if (proto == IPPROTO_UDP && PORT_IS_EPHEMERAL(port))
 		goto epoll_add;
 
 	if (bind(fd, sa, sl) < 0) {
 		/* We'll fail to bind to low ports if we don't have enough
 		 * capabilities, and we'll fail to bind on already bound ports,
-		 * this is fine.
+		 * this is fine. If this isn't the socket with the lowest number
+		 * for a given protocol, leave it open, to avoid unnecessary
+		 * holes in the numbering.
 		 */
-		close(fd);
-		return 0;
+		if ((proto == IPPROTO_TCP && fd == c->tcp.fd_min) ||
+		    (proto == IPPROTO_UDP && fd == c->udp.fd_min) ||
+		    ((proto == IPPROTO_ICMP || proto == IPPROTO_ICMPV6) &&
+		     fd == c->icmp.fd_min)) {
+			close(fd);
+			return 0;
+		}
+		return fd;
 	}
 
 	if (proto == IPPROTO_TCP && listen(fd, 128) < 0) {

util.h

@@ -23,6 +23,7 @@ void debug(const char *format, ...);
 	} while (0)
 
 #define MIN(x, y)		(((x) < (y)) ? (x) : (y))
+#define MAX(x, y)		(((x) > (y)) ? (x) : (y))
 
 #define IN_INTERVAL(a, b, x)	((x) >= (a) && (x) <= (b))